Analogic AAT1217 600ma, 1.2mhz, micropower synchronous step-up converter Datasheet

AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
General Description
The AAT1217 a high efficiency, synchronous, fixed
frequency, step-up converter designed for singlecell or dual-cell alkaline, NiMH, or NiCd batterypowered applications. The high 1.2MHz switching
frequency and completely integrated control circuitry minimize the total solution footprint area
while maintaining excellent regulation, ripple, and
transient response throughout the full load range.
Pulse skipping mode operation and low quiescent
current allow the AAT1217 to maintain high efficiency performance for light load and sleep mode
conditions. With a 1.2A peak switch current limit,
the AAT1217 is capable of delivering 100mA to the
load from a single AA cell or up to 400mA from dual
AA cells. The AAT1217 has a 0.85V start-up voltage with operation down to 0.5V.
The AAT1217 is available in a Pb-free, space-saving low profile (1mm) 6-pin TSOT23 package and
is rated over the -40°C to +85°C ambient temperature range.
SwitchReg™
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
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VIN Operation Range: 0.5V to VOUT
VOUT Range: 2.5V to 5.5V
100mA Output from a Single AA Cell Input
400mA Output from a Dual AA Cell Input
High Efficiency: Up to 93% Efficiency
Low Start-Up Voltage: 0.85V Typical
Internal Synchronous Rectifier
— VOUT ≤ 4.5V: No External Schottky Diode
Fixed Frequency Pulse Width Modulation
(PWM) Current-Mode Control Scheme with
Internal Compensation
1.2MHz Fixed Switching Frequency
1.2A Current Limit
Light Load Pulse Skipping Mode Operation
Low 80µA No Load Input Current
Over-Current Protection
EMI Reduction Anti-Ringing Control Circuitry
Low Shutdown Current: <1.0µA
-40°C to +85°C Ambient Temperature Range
Low Profile (1mm) TSOT23-6 Package
Applications
•
•
•
•
•
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Cellular and Smart Phones
Digital Still and Video Cameras
Microprocessors and DSP Core Supplies
MP3 Player
Portable Instruments
Wireless and DSL Modems
Typical Application
L1
4.7µH
L1
4.7µH
VIN: 0.85V
C IN
4.7µF
R3
1MΩ
1217.2007.07.1.0
VIN
SW
VOUT
AAT1217-1.2
SHDN
GND
FB
VOUT:
3.3V,100 mA
R1
1.02MΩ
R2
604kΩ
C OUT
4.7µF
VIN: 0.85V
C IN
4.7µF
R3
1MΩ
VIN
SW
VOUT
AAT1217-3.3
SHDN
GND
FB
VOUT:
3.3V,100 mA
C OUT
4.7µF
1
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
Pin Descriptions
Pin #
Symbol
2
3
GND
FB
4
SHDN
5
6
VOUT
VIN
1
SW
Function
Power Switch Pin. Ties to the drains of the PMOS synchronous rectifier and the
NMOS switch.
Ground Pin
Feedback Input Pin. Connect FB to the center point of the external resistor divider.
The feedback threshold voltage is 1.23V.
Shutdown Signal Input. Logic high enables the IC. Logic low disables the IC. Shutdown
current is <1µA.
Power Output Pin. Tied to the source of the PMOS synchronous rectifier.
Power Supply Input. Must be closely decoupled to GND, Pin 2, with a 4.7µF or greater
ceramic capacitor.
Pin Configuration
TSOT23-6
(Top View)
SW
GND
FB
2
1
6
2
5
3
4
VIN
VOUT
SHDN
1217.2007.07.1.0
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
Absolute Maximum Ratings1
Symbol
VIN
VSW
VFB, VSHDN
VOUT
TA
TSTORAGE
TLEAD
TJ
Description
Input Supply Voltage
SW Voltage
FB, SHDN Voltages
VOUT Voltage
Operating Ambient Temperature Range2
Storage Temperature Range
Lead Temperature (Soldering, 10s)
Operating Junction Temperature Range2
Thermal Information3
Symbol
θJA
PD
Description
Maximum Thermal Resistance
Maximum Power Dissipation
Value
Units
Value
Units
-0.3 to 6
-0.3 to 6
-0.3 to 6
-0.3 to 6
-40 to 85
-65 to 150
300
-40 to 150
190
526
V
V
V
V
°C
°C
°C
°C
°C/W
mW
1. Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.
2. TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + PD x θJA.
3. Mounted on an FR4 board.
1217.2007.07.1.0
3
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
Electrical Characteristics1
VIN = 1.2V, VOUT = 3.3V, TA = 25°C, unless otherwise noted.
Symbol
VIN
VOUT
VFB
Description
Minimum Start-Up Voltage
Minimum Operating Voltage
Output Voltage Range
Output Voltage Accuracy3
Reference Voltage
∆VOUT/VOUT/
∆VIN
Reference Voltage Line
Regulation
∆VOUT/VOUT/
∆IOUT
Reference Voltage Load
Regulation
IQ
ILNMOS
ILPMOS
RDS(ON)L
RDS(ON)H
ICL
∆t(ICL)
DMAX
FOSC
VSHDN
ISHDN
TSD
Quiescent Current (Shutdown)
Quiescent Current (Active)
Quiescent Current (Active)
NMOS Switch Leakage
PMOS Switch Leakage
NMOS Switch ON Resistance
PMOS Switch ON Resistance
NMOS Current Limit
Current Limit Delay to Output
Maximum Duty Cycle
Switching Frequency
SHDN Input Low
SHDN Input High
SHDN Input Current
Thermal Shutdown
Conditions
IOUT = 1mA
VSHDN = VIN
IOUT = 10mA; TA = -40°C to +85°C
TA = -40°C to +85°C
VIN = 1.2V to 2.4V, IOUT = 10mA,
VOUT = 3.3V
VIN = 2.4V to 4.2V, IOUT = 10mA,
VOUT = 5.0V
VIN = 1.2V, IOUT = 10mA to 100mA
VOUT = 3.3V
VIN = 3.6V, IOUT = 10mA to 400mA
VOUT = 5.0V
VSHDN = 0
VIN = 1.8V, Current from input voltage
source. VSHDN = VIN
Measured on VOUT, VSHDN = VIN
VSW = 5V
VSW = 0V
VOUT = 3.3V
VOUT = 5V
VOUT = 3.3V
VOUT = 5V
VFB = 1.15V, TA = -40°C to +85°C
TA = -40°C to +85°C
VSHDN = 5.5V
Hysteresis
Min
2.5
-4
1.192
Typ
0.85
0.5
1.230
0.2
Max
1
0.65
5.5
+4
1.268
0.003
750
80
0.9
1.00
1
300
0.1
0.1
0.35
0.30
0.60
0.55
1200
40
85
1.2
500
5
5
0.01
160
20
V
%
V
%/mA
0.01
115
V
%/V
0.4
0.004
Units
µA
µA
µA
Ω
Ω
1.5
0.35
1
mA
ns
%
MHz
V
µA
°C
1. Specifications over the temperature range are guaranteed by design, characterization, and correlation with statistical process controls.
2. Not including the current into internal resistance divider.
3. For fixed 3.3V and 5.0V output voltage version. The adjustable output voltage is guaranteed by reference voltage accuracy.
4
1217.2007.07.1.0
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
Typical Characteristics
Efficiency vs. Output Current
Efficiency vs. Output Current
(VOUT = 3.3V; TA = 25°°C)
(VOUT = 5V; TA = 25°
°C)
100
100
90
VIN = 3.6V
80
Efficiency (%)
Efficiency (%)
VIN = 2.4V
90
VIN = 2.4V
80
70
VIN = 1.5V
60
50
VIN = 1.2V
40
30
70
40
30
20
10
10
1
10
100
VIN = 1.5V
50
20
0
0.1
VIN = 1.2V
60
0
0.1
1000
1
Output Current (mA)
1000
Output Voltage vs. Output Current
(VOUT = 3.3V; TA = 25°°C)
(VOUT = 5V; TA = 25°°C)
3.5
5.2
Output Voltage (V)
Output Voltage (V)
100
Output Current (mA)
Output Voltage vs. Output Current
3.4
VIN = 2.4V
VIN = 1.5V
VIN = 1.2V
3.3
3.2
5.1
VIN = 1.2V
VIN = 2.4V
VIN = 1.5V
5
VIN = 3.6V
4.9
4.8
3.1
0
100
200
300
400
500
0
600
100
Output Current (mA)
200
300
400
500
600
Output Current (mA)
Minimum Start-Up Voltage vs. Output Current
Maximum Output Current vs. Input Voltage
(VOUT = 3.3V; TA = 25°
°C)
(L = 4.7µH; TA = 25°°C)
1000
1.5
1.35
Maximum Output
Current (mA)
Start-Up Voltage (V)
10
1.2
1.05
0.9
0.75
0.6
0
20
40
60
80
100
120
140
Output Current (mA)
1217.2007.07.1.0
160
180
200
800
VOUT = 3.3V
600
VOUT = 5V
400
200
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Input Voltage (V)
5
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
Typical Characteristics
No Load Input Current vs. Input Voltage
Output Voltage vs. Temperature
150
3.35
140
3.34
Output Voltage (V)
Input Current (µA)
(VOUT = 3.3V; TA = 25°°C; No Load)
130
120
110
100
90
80
70
3.33
3.32
3.31
3.3
3.29
3.28
3.27
60
3.26
50
1.5
3.25
-50
1.8
2.1
2.4
2.7
3
-25
0
25
50
75
Temperature (°°C)
Input Voltage (V)
Pulse Skipping Mode Operation
Anti-Ringing Operation at SW
(VIN = 1.8V; VOUT = 3.3V; IOUT = 5mA)
(VIN = 2.4V; VOUT = 5V; IOUT = 20mA)
VSW
2V/div
100
VSW
2V/div
0V
0V
VOUT
50mV/div
(AC)
Time (1ms/div)
Time (400ns/div)
Load Transient Response
(VIN = 1.5V; VOUT = 3.3V; CFF = 100pF)
IOUT
50mA/div
100mA
40mA
0A
VOUT
100mV/div
(AC)
Time (100µs/div)
6
1217.2007.07.1.0
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
Functional Block Diagram
VIN
VIN
L1
+
–
SW
Slope
Compensation
MUX
VOUT
GOOD
2.3V
–
VOUT
Current
Sense
CIN
FB
Antiringing
Control
To VIN
Bandgap
1.23V
+
–
+
EA
SHDN
–
Comp
Shutdown
Control
Functional Description
The AAT1217 is a synchronous step-up DC-DC converter. It utilizes internal MOSFET switches to
achieve high efficiency over the full load current
range. It operates at a fixed switching frequency of
1.2MHz, and uses the slope compensated current
mode pulse width modulation (PWM) architecture.
The device can operate with an input voltage below
1V; the typical start-up voltage is 0.85V.
Synchronous Rectification
The AAT1217 integrates a synchronous rectifier to
improve efficiency as well as to eliminate the need
for an external Schottky diode. The synchronous
rectifier is used to reduce the conduction loss contributed by the forward voltage of an external
Schottky diode. The synchronous rectifier is realized by a P-channel MOSFET (PMOS) with gate
1217.2007.07.1.0
+
Start-Up
Oscillator
COUT
VOUT
R1
R2
PWM
Logic
GND
Oscillator
1.2MHz
control circuitry that incorporates relatively complicated timing concerns. An external Schottky diode
is required when the output voltage is greater than
4.5V.
Low Voltage Start-Up
The AAT1217 can start-up with supply voltages
down to 0.85V. During start-up, the internal low
voltage start-up circuitry controls the internal
NMOS switch. The AAT1217 leaves the start-up
mode once VOUT exceeds 2.3V. An internal comparator (VOUT GOOD) monitors the output voltage
and places the chip into normal operation once
VOUT exceeds 2.3V. The AAT1217’s control circuitry is biased by VIN during start-up and biased by
VOUT once VOUT exceeds VIN. When VOUT exceeds
VIN, the AAT1217’s operation will be independent
of VIN.
7
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
Current Mode Operation
The AAT1217 is based on a slope compensated
current mode PWM control topology. It operates at
a fixed frequency of 1.2MHz. At the beginning of
each clock cycle, the main switch (NMOS) is turned
on and the inductor current starts to ramp. After the
maximum duty cycle or the sense current signal
equals the error amplifier (EA) output, the main
switch is turned off and the synchronous switch
(PMOS) is turned on. This control topology features cycle-by-cycle current limiting which can prevent the main switch from overstress and the external inductor from saturating.
Pulse Skipping Mode Operation
At very light load, the AAT1217 automatically
switches into pulse skipping mode operation to
improve efficiency. During this mode, the PWM
control will skip some pulses to maintain regulation.
If the load increases and the output voltage drops,
the device will automatically switch back to normal
PWM mode and maintain regulation.
Anti-Ringing Control
An anti-ringing circuitry is included to remove the
high frequency ringing that appears on the SW pin
when the inductor current goes to zero. In this
case, a ringing on the SW pin is induced due to
remaining energy stored in parasitic components of
switch and inductor. The anti-ringing circuitry
clamps the voltage internally to the battery voltage
and therefore dampens this ringing.
Device Shutdown
When SHDN is set logic high, the AAT1217 is put
into active mode operation. If SHDN is set logic
low, the device is put into shutdown mode and consumes less than 1µA of current. After start-up, the
internal circuitry is supplied by VOUT, however, if
shutdown mode is enabled, the internal circuitry
will be supplied by the input source again.
8
Application Information
Adjustable Output Voltage
An external resistor divider is used to set the output
voltage. The output voltage of the switching regulator (VOUT) is determined by the following equation:
R1

VOUT = 1.23V · 1 + R2


Table 1 lists the recommended resistor values for
particular output voltage settings.
VOUT
3.3V
5.0V
Ω)
R1(Ω
1.02M
1.02M
Ω)
R2(Ω
604k
332k
Table 1: Resistor Selection for Output Voltage
Setting.
Fixed Output Voltage
AAT1217 has two fixed output voltage options:
3.3V and 5V. An internal resistor divider is connected to the FB pin inside the package which eliminates the need for external feedback resistors.
When designing with the fixed output voltage
option, remember to leave the FB pin open; otherwise the output voltage will be affected. However, a
feed-forward capacitor can still be added between
the FB and VOUT pins to enhance the control loop
performance.
Inductor Selection
The high switching frequency of 1.2MHz allows for
small surface mount inductors. For most applications, the AAT1217 operates with inductors from
2.2µH to 10µH. Use the following equations to
select the proper inductor value for a particular
application condition:
1217.2007.07.1.0
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
∆IL
IPEAK = IDC + 2
IDC =
IPEAK =
IOUT · VOUT
η · VIN
∆IL =
VIN · D
VOUT - VIN
; D=
L · FSW
VOUT
∆IL =
VIN · (VOUT - VIN)
L · FSW · VOUT
VIN · (VOUT - VIN)
IOUT · VOUT
η · VIN + 2L · FSW · VOUT
IPEAK Peak Inductor Current
IDC DC Component (Average) of the Inductor
Current
∆IL Peak-Peak Inductor Ripple Current
IOUT Output (Load) Current
VOUT Output Voltage
VIN Input Voltage
η
AAT1217 Efficiency (consult the performance graphs in the “Typical Characteristics”
section of the data sheet)
D
Steady-State Duty Cycle
FSW Switching Frequency
L
Inductor Value
For a given chosen inductor value and application
conditions make sure the peak inductor current does
not exceed the maximum current rating of the selected vendor’s inductor. For optimum load transient and
efficiency, low DCR inductors should be selected.
Table 2 lists some typical surface mount inductors
that are suitable for typical AAT1217 applications.
1217.2007.07.1.0
Input Capacitor
A surface mount 4.7µF or greater, X5R or X7R,
ceramic capacitor is suggested for the input capacitor. The input capacitor provides a low impedance
loop for the edges of pulsed current drawn by the
AAT1217. Low ESR/ESL X7R and X5R ceramic
capacitors are ideal for this function. To minimize
stray inductance, the capacitor should be placed
as close as possible to the IC. This keeps the high
frequency content of the input current localized,
minimizing EMI and input voltage ripple. Always
examine the ceramic capacitor DC voltage coefficient characteristics to get the proper value. For
example, the capacitance of a 10µF, 6.3V, X5R
ceramic capacitor with 5.0V DC applied is actually
about 6µF.
A laboratory test set-up typically consists of two long
wires running from the bench power supply to the
evaluation board input voltage pins. The inductance
of these wires, along with the low-ESR ceramic input
capacitor, can create a high Q network that may
affect converter performance. This problem often
becomes apparent in the form of excessive ringing
in the output voltage during load transients which
can produce errors in loop phase and gain measurements. Since the inductance of a short printed
circuit board (PCB) trace feeding the input voltage is
significantly lower than the power leads from the
bench power supply, most actual applications do not
exhibit this problem. In applications where the input
power source lead inductance cannot be reduced to
a level that does not affect the converter performance, a high ESR tantalum or aluminum electrolytic
capacitor should be placed in parallel with the low
ESR, ESL bypass input ceramic capacitor. The introduction of the high ESR capacitor dampens the high
Q network and stabilizes the AAT1217.
9
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
Part Number
Sumida CDH28D11/S
Coiltronics SD3112
TDK VLF3012A
Sumida CR43
Sumida CDRH4D28
Toko D53LC
L (µH)
2.2
4.7
10
2.2
4.7
10
2.2
4.7
10
2.2
4.7
10
2.2
4.7
10
4.7
10
Output Capacitor
Ω)
Max DCR (mΩ
123
238
431
140 (typ)
246 (typ)
446 (typ)
100
190
410
71.2
108.7
182
31.3
72
128
45
90
In addition, the output voltage droop during load
transient is dominated by the capacitance of the
ceramic output capacitor. During a step increase in
load current, the ceramic output capacitor alone
supplies the load current until the loop responds.
Within several switching cycles, the loop responds
and the inductor current increases to match the
load current demand. Larger output capacitor values help to reduce the voltage droop during large
load current transients.
An external Schottky diode is required when the
output voltage is above 4.5V. The Schottky diode is
optional for output voltages ≤ 4.5V, but can
improve efficiency by about 2% to 3%.
10
1.15
0.75
0.53
1.12
0.8
0.55
1
0.74
0.49
1.75
1.15
1.04
2.04
1.32
1
1.87
1.33
Size WxLxH (mm)
3x3.3x1.2
3.1x3.1x1.2
2.8x2.6x1.2
4.3x4.8x3.5
5.0x5.0x3.0
5.0x5.0x3.0
Table 2. Typical Surface Mount Inductors.
The output capacitor limits the output ripple and provides holdup during large load transitions. A 4.7µF to
10µF, X5R or X7R, ceramic capacitor is suggested
for the output capacitor. Typically the recommended
capacitor range provides sufficient bulk capacitance
to stabilize the output voltage during large load transitions and has the ESR and ESL characteristics
necessary for low output voltage ripple.
External Diode Selection
Rated DC Current (A)
Load Disconnect in Shutdown
In conventional synchronous step-up converters, a
conduction path exists from input to output through
the backgate (body diode) of the P-channel MOSFET during shutdown. Special application circuitry
can disconnect the load from the battery during
shutdown (see Figure 1).
PCB Layout Guidance
The AAT1217 typically operates at 1.2MHz. This is a
considerably high frequency for DC-DC converters.
PCB layout is important to guarantee satisfactory
performance. It is recommended to make traces of
the power loop, especially where the switching node
is involved, as short and wide as possible. First of
all, the inductor, input and output capacitor should
be as close as possible to the device. Feedback and
shutdown circuits should avoid the proximity of large
AC signals involving the power inductor and switching node. The optional rectifier diode (D1 in Figure
1) can improve efficiency and alleviate the stress on
the integrated MOSFETs. The diode should also be
close to the inductor and the chip to form the shortest possible switching loop. While the two-layer PCB
shown in Figures 2 and 3 is enough for most applications, large and integral multi-layer ground planes
1217.2007.07.1.0
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
Figure 1 is the schematic for a highly efficient load
disconnect application circuit for the AAT1217. An
example PCB layout for the AAT1217 is shown in
Figures 2 and 3.
are ideal for high power applications. Large areas of
copper have lower resistance and help to dissipate
heat. The converter's ground should join the system
ground to which it supplies power at one point only.
D1
MBR0520
L1
4.7µH
1
VIN 0.85V
CIN
4.7µF
6
4
VIN
SW
AAT1217
SHDN
VOUT
FB
GND
5
3
VOUT
3.3V,100mA
Q1
Si2305 DS
R4
510kΩ
R1
1.02MΩ
R2
604kΩ
2
ON/OFF Control
R3
510kΩ
COUT
4.7µF
Q2
2N3904
Figure 1. AAT1217 High Efficiency Load Disconnect Application Circuit
Figure 2. AAT1217 Evaluation Board Layout
Example Top Layer
1217.2007.07.1.0
Figure 3. AAT1217 Evaluation Board Layout
Example Bottom Layer
11
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
Ordering Information
Output Voltage1
Package
Adj.
Fixed 3.3V
Fixed 5.0V
Marking2
TSOT23-6
TSOT23-6
TSOT23-6
Part Number (Tape and Reel)3
AAT1217ICA-1.2-T1
AAT1217ICA-3.3-T1
AAT1217ICA-5.0-T1
VZMYY
WAMYY
WBMYY
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semiconductor products that are in compliance with current RoHS standards, including
the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more
information, please visit our website at http://www.analogictech.com/pbfree.
Package Information
TSOT23-6
Part Dimensions
0.40 ± 0.10
0.95 BSC
0.127 BSC
1.60 BSC
2.80 BSC
Detail "A"
End View
Top View
1.00 ± 0.10
0.25 BSC
2.90 BSC
+10°
-0°
0.45 ± 0.15
0.000
All dimensions in millimeters.
1.00
+ 0.100
- 0.000
Side View
Detail "A"
1. Please contact sales for other voltage options.
2. YY = Manufacturing Date Code.
3. Sample stock is generally held on part numbers listed in BOLD.
12
1217.2007.07.1.0
AAT1217
600mA, 1.2MHz, Micropower
Synchronous Step-Up Converter
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copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the
customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty.
Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated.
All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737- 4600
Fax (408) 737- 4611
1217.2007.07.1.0
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